RU77633U1 - DEVICE FOR ELECTROCHEMICAL DESTRUCTION OF A PIPE PART IN A WELL - Google Patents

Abstract

The utility model relates to the oil and gas industry and can be used in the construction, operation and liquidation of wells, for the destruction of a section of a casing pipe in a well, when drilling sidetracks, isolating produced water and eliminating the well itself. The essence of the proposed utility model is that the design of the device wedge contact node, in contrast to the prototype, allows you to achieve reliable hard contact with the surface of the casing, which prevents welding retractable cont active wedges with casing and ensures reliable operation of the electrochemical cell (device - casing) at current values of 10-15 kA / h or more, which will ensure the dissolution of the metal more than 10-15 kg / h. In addition, the contact node simultaneously performs the functions of the upper centralizer and the fixture of the device in the working interval. The presence of a compensator for the length of the pressure column, unlike the prototype, allows you to remove the load on the wedge contact node and prevent vertical movements of the device, which increases the efficiency of the electrochemical process and reduces the time of dissolution of the metal in a given interval. The use of a cylindrical body of the electrical unit as a cathode, unlike the prototype, allows to reduce the diameter of the device and thereby expand its scope (for pipes of smaller diameter). The presence of the inner tube, in contrast to the prototype, allows for additional heat transfer to cool the transformer and parts of the electrical unit of the current transducer when pumping electrolyte through it. This ensures stability.

Description

The utility model relates to the oil and gas industry and can be used in the construction, operation and liquidation of wells, for the destruction of the casing section in the well, when drilling sidetracks, isolating formation water and eliminating the well itself.

Closest to the claimed utility model is a device for destroying a pipe section in a well according to patent RU No. 2227201, including an arrangement in the form of a tubular casing with a housing located inside it and an opening for electrolyte exit, sealing cuffs, anode and ring cathode, which is equipped with a bus and centralizers , the tubular casing has a connecting sleeve for fastening to the string of tubing, the housing is sealed, at least two-piece and placed on the centering sleeves, inside the housing a current transformer and a transformer are placed, while the casing is equipped with a hermetic input of the power cable, hermetic terminals on the ring cathode, which is located on the casing and isolated from it, and on the anode, the cathode length being determined by the length of the pipe section being destroyed, the output to the anode passes through the bus to centralizers that simultaneously perform the function of contacts with the pipe, the housing sections are equipped with seals, for example, of the labyrinth type, the sealing cuffs of the device are made in the form of cup-shaped elastic cuffs, located x cups above and below the destruction of the pipe section to form an electrochemical cell with an annular cathode and an inner pipe wall — an active zone communicated through an electrolyte outlet with an annular space between the casing and the casing to organize the pumping of electrolyte supplied from the surface through the tubing pipes on which the cable is fixed.

The disadvantages of this device are:

- the use of a spring centralizer as a current-transmitting contact with the casing;

Due to the small clamping force, the centralizer springs do not provide reliable hard contact with the casing surface, especially in the presence of irregularities on the surface and the film of corrosion products. Therefore, even with relatively small current values (50-100 A / h), the springs will be welded to the inner surface of the pipe, which creates an emergency situation when removing the device to the surface. Inability to transfer current of 1000 A / h or more.

- the presence of cup-shaped cuffs located above and below the device with the cups up;

The upper cuff unnecessarily increases the hydraulic resistance during pumping of the electrolyte, reduces the flow rate and the upward flow rate of the electrolyte, which can lead to the deposition of mechanical impurities and iron hydroxides in the working area between the cathode of the device and the (anode) casing, which sharply reduces the efficiency of the electrochemical process of anodic dissolution of the metal. The lower cuff contributes to the accumulation of sludge from mechanical impurities of the electrolyte and products of the electrochemical process, for example, iron hydroxide, which can lead to plug formation and complication in the form of sticking of the device in the well. In addition, the low speed of pumping of the electrolyte (up to 0.05 l / s) does not provide flow turbulence and leads to the formation of stagnant zones in the working section, which also reduces the efficiency of the device.

- lack of a fixing unit and a temperature compensator in the design;

Temperature and hydraulic changes (lengthening, reduction) of the length of the pressure column (from a few centimeters to 1 m or more) during the pumping of the electrolyte will not allow working in the specified interval

due to vertical movements (up, down) of the device, which will sharply reduce the efficiency of the anodic dissolution of the metal, increase the duration of the process and may lead to damage to the device when welding the centralizer springs to the casing pipe.

- insufficient heat removal with an electrical component, since heat transfer occurs only along the external generatrix of the device and at low electrolyte consumption and air filling of the internal volume, can lead to overheating and failure of the transformer and electrical components.

- unreliability of the design and the narrow scope of the device.

This is due to the remote ring cathode, which when descent into the well of the device can be crushed and shorted to the housing. With an increase in the cathode wall thickness, the device cannot be used in pipes with an inner diameter of less than 160 mm.

The above disadvantages dramatically reduce the operability of the device (reliability), the efficiency of the electrochemical process and the scope.

The technical result of the proposed utility model is to increase the efficiency of the device and expand its scope.

This technical result is achieved by solving a technical problem aimed at improving the manufacturability of the device.

The stated technical problem is solved due to the fact that in the known device for electrochemical destruction of a pipe section in a well containing a mounting unit of the device to a column of pressure pipes, a cylindrical body of an electrical unit with upper and lower covers with a sealed cable entry, an electrolyte outlet and placed in it with a transformer and a current transducer block, an anode and a cathode, and the length of the cathode corresponds to the length of the destroyed section of the pipe, which also contains the upper and lower centralizers, roystvo

additionally equipped with a compensator for the length of the column of pressure pipes, a wedge contact assembly, including sliding contact wedges and a hydraulic piston-pusher of the electrical assembly, while the contact assembly is simultaneously the top centralizer and the fixture of the device in the working position, and the cylindrical housing of the electrical assembly is also the cathode, the upper and the lower cover is connected to the cathode body by inserts of dielectric material, a pumping tube is located inside the body of the electrical unit electrolyte and sealing septum, the lower housing cover is provided with at least two openings for the electrolyte and the electrolyte flow swirlers, and by means of a threaded connection to it is fixed rigidly to the respective lower centralizer diameter of the casing.

The proposed device is illustrated by drawings of figure 1, figure 2, figure 3. Figure 1 shows the device in the transport position. Figure 2 - the device is in the working position. Figure 3 is a section along aa of the wedge contact node.

The device consists of a sub 1 for attaching it to a column of pressure pipes (BT, tubing, etc.), a compensator for the length of the column of pressure pipes 2, a wedge contact assembly 3, including sliding contact wedges 4 and a hydraulic piston-pusher 5, of an electrical assembly 6, consisting from a cylindrical body - cathode 7, upper cover 8 and lower cover 9, connected to the body - cathode by inserts 10 made of a dielectric material (for example, fluoroplastic). In the top cover 8 there is a sealed cable entry 11 for the electric cable 12. Inside the electrical unit 6 there is a pipe 13 for pumping electrolyte, a power transformer 14, a current transducer block 15 and a sealing partition 16. For heat exchange, the internal cavity of the electrical unit is filled with transformer oil of the calculated volume with given its thermal expansion. At the bottom

the cover 9 has openings 17 for the exit of the electrolyte and swirls of the flow of electrolyte 18. Using a threaded connection, the lower centralizer 19 is rigidly attached to it under the corresponding inner diameter of the casing 20.

The essence of the proposed utility model is that the presence of a wedge contact assembly in the device design, in contrast to the prototype, makes it possible to achieve reliable hard contact with the surface of the casing pipe, which prevents welding of sliding contact wedges with the casing pipe and ensures reliable operation of the electrochemical cell (device - casing string) at currents of 10-15 kA / h or more, which will ensure the dissolution of the metal more than 10-15 kg / h. In addition, the contact node simultaneously performs the functions of the upper centralizer and the fixture of the device in the working interval. The presence of a compensator for the length of the pressure column, unlike the prototype, allows you to remove the load on the wedge contact node and prevent vertical movements of the device, which increases the efficiency of the electrochemical process and reduces the time of dissolution of the metal in a given interval.

The use of a cylindrical body of the electrical unit as a cathode, unlike the prototype, allows to reduce the diameter of the device and thereby expand its scope (for pipes of smaller diameter).

The presence of the inner tube, in contrast to the prototype, allows for additional heat transfer to cool the transformer and parts of the electrical unit of the current transducer when pumping electrolyte through it. This ensures the stability of the electrical component for a long time (more than 24 hours), necessary for complete dissolution of the metal in the casing section, located opposite the cathode casing.

The presence of flow swirls on the bottom cover, unlike the prototype, allows to turbolize the upward flow of electrolyte and thereby avoid stagnant zones and increase the efficiency of the electrochemical process due to a more complete removal of hydrogen bubbles formed at the cathode.

The device operates as follows (see figures 1, 2, 3).

Before starting work, the pipe section to be destroyed is worked out with mechanical scrapers and treated with a 5-10% solution of hydrochloric (HC1) or other acid to remove salt deposits and corrosion products. After that, by means of an adapter 1, the device is attached to the column of pressure pipes 2 (BT, tubing, etc.) and descends simultaneously with the electric cable 12 into the well to a predetermined depth, where it is supposed to destroy (dissolve) the section of the casing pipe 20. At the same time, the length of the section to be destroyed the casing will correspond to the length of the cathode-casing of the device, which is selected in advance, based on the task.

Then, with surface aggregates, under the pressure necessary to overcome the hydraulic resistance in the well (usually from 1.0 to 8.0 MPa depending on depth), an electrolyte is fed, for example, an aqueous solution of sodium chloride (NaCl) with a flow rate that provides sufficient heat removal with the electrical part of the device and the speed in the annular space "device - casing pipe", providing the removal of mechanical impurities, products of the electrochemical process - hydroxides of iron (metal) and the breakdown of hydrogen formations from the surface of the body a cathode. According to calculations and experimental data, for various thermobaric and structural conditions, the working flow rate of the electrolyte will be from 0.5 to 5.0 l / s.

When pumping electrolyte through holes 17 of a small (calculated) diameter, a pressure differential is created between the internal cavity

device and downhole, which ensures the extension of the wedges 4 by means of a piston - pusher 5 (see figure 2, 3). Depending on the magnitude of the pressure drop, the clamping force of the current-transmitting wedges - contacts to the casing can reach 200-300 kg or more, which, unlike the prototype, provides reliable contact with the casing, which allows working on a current of large magnitude.

After the circulation of the electrolyte in the borehole from the ground-based direct current source through cable 12, electric current is supplied to the device and the anodic dissolution of the metal from the removed section of the pipe begins in the electrochemical cell - the active zone “cathode of the device - electrolyte - casing pipe (anode)”. With the complete destruction (dissolution) of a given section of the pipe, the flow of electric current in the circuit automatically stops, as judged by the control devices installed on the surface.

Then, backward pumping of the electrolyte through the annulus creates a pressure drop on the internal cavity of the device, while the piston-pusher 5 returns to its original transport position. After that, by lifting the device, the contact wedges are returned to the transport position and the cable and cable are removed to the surface. If necessary, the electrolyte is replaced with a process fluid before lifting.

To destroy the pipe section with a length exceeding the length of the cathode of the device, the operation is repeated with the necessary multiplicity by moving the device up vertically, without lifting it to the surface.

Using the proposed device provides the following advantages:

- conduct the process of anodic electrochemical dissolution of the casing section at a current value in excess of 10,000 - 15,000 A / h;

- work at an upward flow rate of the electrolyte,

providing removal of mechanical impurities and metal hydroxides from the working area;

- lead the process of dissolution of the pipe section in a strictly specified interval;

- increased reliability of the device provides stability and efficiency of the electrochemical process;

- extended scope.

Estimated economic effect, depending on the depth of work, the wall thickness of the casing and the length of the destroyed area will be from 200 to 800 thousand rubles per well / operation.

Claims (1)

A device for electrochemical destruction of a pipe section in a well, comprising a unit for attaching the device to a column of pressure pipes, a cylindrical body of an electrical unit with upper and lower covers with a sealed cable entry, an electrolyte outlet and a transformer and a current transducer block, an anode and a cathode placed therein, moreover, the length of the cathode corresponds to the length of the destroyed section of the pipe, containing also upper and lower centralizers, characterized in that the device is additionally equipped with a compensator for the columns of the pressure pipes, a wedge contact assembly including sliding contact wedges and a hydraulic piston-pusher of the electrical assembly, the contact assembly being simultaneously the top centralizer and the fixture of the device in the working position, and the cylindrical housing of the electrical assembly is simultaneously the cathode, the upper and lower covers are connected with a cathode casing with inserts of dielectric material, inside the casing of the electrical unit there is a pipe for pumping electrolyte and a sealing burnout The bottom cover of the housing is made with at least two openings for the exit of electrolyte and swirls of the flow of electrolyte, and by means of a threaded connection, the lower centralizer is rigidly attached to it under the corresponding diameter of the casing.